Thoughts on Virtual Machines

I have been recently diving head first into the realm of virtual machines, deploying them in a small - medium sized network. I've written about the life and times of the migration in other posts, so I won't go into full blown details here, but what was interesting was to see how well a DC and an Exchange server would perform in the virtual environment, in addition to an ACT server for a particular add in they had purchased. We are using Server 08 x64 bit on dell hardware, 32 gb of ram, and 15k drives to run the host OS and the 3 servers. In addition, we required that a DRAC (read: Dell Remote Access Card) card be installed as part of the package, just in case. Exchange 2007 sp2, and server 08 (both standard and R2) were used. The verdict: Wonderful! All 3 servers are coexisting beautifully, and working as if they were on their own hardware. I was pleasantly surprised to find that each server performed particularly well, and enjoyed the new GUI's related to server 08. (Which, for those who have not moved to the new 08 server yet, be prepared for a learning curve...) Here's what I noticed as "interesting": 1] The virtual machine manager on the base machine works as expected. If you've ever played with the Virtual PC from Microsoft, the look/feel is somewhat similar, from my experience. I LOVE the flexibility of assigned hardware, ram, etc, on the fly. (Though not everything can be done until you shut the VM down.) 2] Recovery of the VM is a cinch. So long as the image that is saved is still a good image, recreation of the machine on the fly has been a true timesaver, not only in the aspect of disaster recovery, but for testing purposes as well. We were able to recreate their whole network in a few hours as a disaster recovery test in the event that the "Worst of the worst" scenario had occurred. 3] Underlying hardware is key thought. Most of the servers we purchase comes with 7.5 k drives. Basic drives that are good for most of the scenarios that we deploy. Not so with the base hardware of a virtual server host. 15k drives are almost a necessity in just about every scenario. We ran into serious hardware performance issues with the 7.5 k drives and realized it just wasn't worth it. The money invested in faster drives is worth it. 4] (almost) Never deploy a TS on a VM. If you consider how much a TS does just during normal functionality, the amount of resources needed can be considerable. We tried to run a TS on a VM that usually had around 30 people logged in a once. BAAAADDDD idea. We watched the performance slow to a crawl, and realized very quickly that was not the way to go. (Not to mention holding my phone 6 inches away from my ear listening to yet another call about the performance...) Luckily we had not removed the old terminal server, so switching people back was easy enough. A ton of stress testing should be done prior to deployment before you consider putting a TS on a VM. 5] A RAC card can save you a very long drive. The server locked up for some reason at 10 pm one evening. A quick reboot of the server was needed to resolve the issue, and because we though about adding the card ahead of time, there was little to no down time. No one actually noticed everything was down, which was a good thing. It's always good to walk up to the owner of a company and say "Oh by the way, did you know..." What other experiences have you had with VM's that might not be the stuff of "Standard fare?" Please share!